After 1804, change came slowly to Spirit Mound. For 55 years the area remained the land of the Yankton Sioux, while fur traders conducted business from posts on the Missouri, and the tallgrass prairie continued to thrive as it had for thousands of years. In 1859 the Yankton moved to a reservation 70 miles upriver, and Congress created Dakota Territory in 1861. The first homestead on Spirit Mound was filed in 1868. A pioneer later recalled that looking north from the top of the mound, he could see only one tree. During the next 100 years, however, the mound changed tremendously as settlers established two farmsteads, planted groves, divided fields with barbed wire, pastured land along the creek, and operated a feedlot on the eastern slope. The prairie habitat disappeared except for a five-acre remnant on the western side. Preservation and restoration also came slowly. In 1986 a local group incorporated the Spirit Mound Trust, dedicated to saving the mound as a public resource. The Trust's determined pursuit of this vision under its long-term president, Larry Monfore, together with the Lewis and Clark Expedition bicentennial, led to the current project. Spirit Mound Historic Prairie arose from a partnership among the Trust, the South Dakota Division of Parks and Recreation, and the National Park Service, and it is intended as a permanent resource for honoring history and enjoying the biological richness of the tallgrass prairie, even if fully recreating the prairie primeval may be impossible.